1. Field of the Invention
The present invention relates to a method and system for real-time monitoring image transmission, and particularly to a method and system for real-time monitoring image transmission that reduces bandwidth used in transmission according to properties of image compression, thereby optimizing network traffic and speeding transmission.
2. Description of the Related Art
Using network techniques to monitor a remote computer or a peripheral device, such as a Keyboard, Video or Mouse (KVM) has become a common monitoring practice. FIG. 1 depicts a conventional remote image monitoring system, which manages clients via a KVM bus of a host 11 (server). Users can use server switches to monitor the image of the computer systems (clients 13 and 14) in the LAN (Local Area Network) and WAN (Wide Area Network) through a network interface 12.
The conventional system employs full screen transmission to transmit the monitored image, i.e., the client (13 or 14) transmits a full image (frame) with or without compression to the server 11 in a fixed frequency (frame/sec). Since the image data is always large, the transmission will need large network bandwidth, thereby resulting in slow network traffic. Thus, the remote object is hard to be real-time monitored.
In addition, another conventional method is performed by dividing a frame into several sub-frames (sub-blocks), and using a detection module to detect and calculate the variations (variant blocks or dynamics blocks) between any two successive frames, and then only transmitting the variation to the server.
For example, a frame of 1027*768 pixels can be divided into 256 sub-blocks, in which each sub-block is 64*48 pixels. FIG. 2A shows two connected variant blocks 21 and 22. In network transmission, if the variant blocks 21 and 22 are encoded individually, the variant blocks 21 and 22 processed under JPEG compression are 785 and 745 bytes respectively, and the amount of transmission is 785+745=1530 bytes. However, if the variant blocks 21 and 22 are combined and encoded, the combined block processed under JPEG compression contains 964 bytes. According to above, the JPEG overhead for each sub-block of 64*48 pixels is 1530−964=500 bytes. Therefore, the ratio of overhead to amount of transmission is 500/1530=33% if two variant blocks 21 and 22 are transmitted at one time, however, the ratio of overhead to amount of transmission is 500/(1530/2)=66% if two variant blocks 21 and 22 are transmitted individually.
FIG. 2B shows four connected variant blocks 21, 22, 23 and 24. Similarly, a frame of 1027*768 pixels is divided into 256 sub-blocks, and each sub-block contains 64*48 pixels. If the variant blocks 21, 22, 23 and 24 are individually encoded in the JPEG format, the variant blocks 21, 22, 23 and 24 will contain 785, 745, 1272, 840 bytes respectively, and the amount of transmission is 785+745+1272+840=3642 bytes. However, if the variant blocks 21, 22, 23 and 24 are combined and then encoded in the JPEG format, the combined block will contain 1966 bytes. In this case, the JPEG overhead can be reduced by 50% if the variant blocks 21, 22, 23 and 24 are combined and then encoded in the JPEG format. Therefore, the network bandwidth needed for transmission of several variant blocks transmitted simultaneously is less than that needed for these variant blocks to be transmitted individually.
Conventional methods do not fully utilize the above properties, and thus result in too much overhead in transmission. Since relationships or interactions may exist between variant blocks such that these variant blocks are connected, and able to be transmitted simultaneously, to reduce network bandwidth.